The long term objectives of this research are to understand the immunochemical basis for the antigenicity and protective capacity of high molecular weight polysaccharide (PS) antigens isolated from culture supernates of Pseudomonas aeruginosa. The specific aims include determination of the chemistry and structure of PS antigens, preparation and testing in animals of both a multivalent vaccine and PS-protein conjugates for safety, immunogenicity and protective capacity, and testing in humans of 4 monovalent PS preparations. In addition, this research will investigate the role of high molecular weight PS in T cell mediated immunity, especially as it relates to the elicitation of a bactericidal factor from human T cells. We will also determine the capability of different isotypes of human antibody to protect neutropenic mice from P. aeruginosa infection. Immunochemical analysis will include gas liquid chromatographic and nuclear magnetic resonance studies of PS antigens. We will evaluate the safety and immunogenicity of the multivalent PS and PS-protein conjugates by injecting animals with the different preparations, analyze their reactions, and test their antibody responses using a radioactive antigen binding assay. In addition, immunized animals will be challenged with live organisms in a number of models relevent to P. aeruginosa infection, including burned and neutropenic states, to document vaccine efficacy. Humans will be immunized with monovalent PS preparations and their antibody responses measured in the radioactive antigen binding and opsonophagocytic assays. The immunology of PS will be investigated by looking at the in vivo and in vitro properties of murine T cell clones that are selected by the ability to kill live organisms in vitro when stimulated by PS antigens. A similar killing mechanism occurs when human T cells are stimulated with heat killed immunotype 1 P. aeruginosa. The murine and human factors involved in killing will be biochemically characterized and compared. Finally, human antibody made in response to PS vaccination will be isolated and fractionated into different isotypes. These will be passively transferred to neutropenic mice to evaluate their ability to protect the mice against challenge. Overall these studies are designed to investigate the vaccine potential of high molecular weight PS and understand the various immunologic effector mechanisms that may be relevant in immunity to P. aeruginosa infections.